Clean up ARM tail calls a bit. They're pseudo-instructions for normal branches.

Also more cleanly separate the ARM vs. Thumb functionality. Previously, the
encoding would be incorrect for some Thumb instructions (the indirect calls).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127637 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 72 insertions, 32 deletions

diff --git a/lib/Target/ARM/ARMAsmPrinter.cpp b/lib/Target/ARM/ARMAsmPrinter.cpp
index 4c9ab3c..784a661 100644
--- a/lib/Target/ARM/ARMAsmPrinter.cpp
+++ b/lib/Target/ARM/ARMAsmPrinter.cpp
@@ -1707,6 +1707,49 @@ void ARMAsmPrinter::EmitInstruction(const MachineInstr *MI) {
     }
     return;
   }
+  // Tail jump branches are really just branch instructions with additional
+  // code-gen attributes. Convert them to the cannonical form here.
+  case ARM::TAILJMPd:
+  case ARM::TAILJMPdND: {
+    MCInst TmpInst, TmpInst2;
+    // Lower the instruction as-is to get the operands properly converted.
+    LowerARMMachineInstrToMCInst(MI, TmpInst2, *this);
+    TmpInst.setOpcode(ARM::Bcc);
+    TmpInst.addOperand(TmpInst2.getOperand(0));
+    // Add predicate operands.
+    TmpInst.addOperand(MCOperand::CreateImm(ARMCC::AL));
+    TmpInst.addOperand(MCOperand::CreateReg(0));
+    OutStreamer.AddComment("TAILCALL");
+    OutStreamer.EmitInstruction(TmpInst);
+    return;
+  }
+  case ARM::tTAILJMPd:
+  case ARM::tTAILJMPdND: {
+    MCInst TmpInst, TmpInst2;
+    LowerARMMachineInstrToMCInst(MI, TmpInst2, *this);
+    TmpInst.setOpcode(ARM::tB);
+    TmpInst.addOperand(TmpInst2.getOperand(0));
+    OutStreamer.AddComment("TAILCALL");
+    OutStreamer.EmitInstruction(TmpInst);
+    return;
+  }
+  case ARM::TAILJMPrND:
+  case ARM::tTAILJMPrND:
+  case ARM::TAILJMPr:
+  case ARM::tTAILJMPr: {
+    unsigned newOpc = (Opc == ARM::TAILJMPr || Opc == ARM::TAILJMPrND)
+      ? ARM::BX : ARM::tBX;
+    MCInst TmpInst;
+    TmpInst.setOpcode(newOpc);
+    TmpInst.addOperand(MCOperand::CreateReg(MI->getOperand(0).getReg()));
+    // Predicate.
+    TmpInst.addOperand(MCOperand::CreateImm(ARMCC::AL));
+    TmpInst.addOperand(MCOperand::CreateReg(0));
+    OutStreamer.AddComment("TAILCALL");
+    OutStreamer.EmitInstruction(TmpInst);
+    return;
+  }
+
   // These are the pseudos created to comply with stricter operand restrictions
   // on ARMv5. Lower them now to "normal" instructions, since all the
   // restrictions are already satisfied.
diff --git a/lib/Target/ARM/ARMFrameLowering.cpp b/lib/Target/ARM/ARMFrameLowering.cpp
index 4ade29c..c99259d 100644
--- a/lib/Target/ARM/ARMFrameLowering.cpp
+++ b/lib/Target/ARM/ARMFrameLowering.cpp
@@ -400,8 +400,8 @@ void ARMFrameLowering::emitEpilogue(MachineFunction &MF,
     // Jump to label or value in register.
     if (RetOpcode == ARM::TCRETURNdi || RetOpcode == ARM::TCRETURNdiND) {
       unsigned TCOpcode = (RetOpcode == ARM::TCRETURNdi)
-        ? (STI.isThumb() ? ARM::TAILJMPdt : ARM::TAILJMPd)
-        : (STI.isThumb() ? ARM::TAILJMPdNDt : ARM::TAILJMPdND);
+        ? (STI.isThumb() ? ARM::tTAILJMPd : ARM::TAILJMPd)
+        : (STI.isThumb() ? ARM::tTAILJMPdND : ARM::TAILJMPdND);
       MachineInstrBuilder MIB = BuildMI(MBB, MBBI, dl, TII.get(TCOpcode));
       if (JumpTarget.isGlobal())
         MIB.addGlobalAddress(JumpTarget.getGlobal(), JumpTarget.getOffset(),
@@ -412,10 +412,12 @@ void ARMFrameLowering::emitEpilogue(MachineFunction &MF,
                               JumpTarget.getTargetFlags());
       }
     } else if (RetOpcode == ARM::TCRETURNri) {
-      BuildMI(MBB, MBBI, dl, TII.get(ARM::TAILJMPr)).
+      BuildMI(MBB, MBBI, dl,
+              TII.get(STI.isThumb() ? ARM::tTAILJMPr : ARM::TAILJMPr)).
         addReg(JumpTarget.getReg(), RegState::Kill);
     } else if (RetOpcode == ARM::TCRETURNriND) {
-      BuildMI(MBB, MBBI, dl, TII.get(ARM::TAILJMPrND)).
+      BuildMI(MBB, MBBI, dl,
+              TII.get(STI.isThumb() ? ARM::tTAILJMPrND : ARM::TAILJMPrND)).
         addReg(JumpTarget.getReg(), RegState::Kill);
     }
 
diff --git a/lib/Target/ARM/ARMInstrInfo.td b/lib/Target/ARM/ARMInstrInfo.td
index 5a5b6eb..d7e3dc8 100644
--- a/lib/Target/ARM/ARMInstrInfo.td
+++ b/lib/Target/ARM/ARMInstrInfo.td
@@ -1408,11 +1408,7 @@ let isCall = 1,
 
 // Tail calls.
 
-// FIXME: These should probably be xformed into the non-TC versions of the
-// instructions as part of MC lowering.
-// FIXME: These seem to be used for both Thumb and ARM instruction selection.
-// Thumb should have its own version since the instruction is actually
-// different, even though the mnemonic is the same.
+// FIXME: The Thumb versions of these should live in ARMInstrThumb.td
 let isCall = 1, isTerminator = 1, isReturn = 1, isBarrier = 1 in {
   // Darwin versions.
   let Defs = [R0, R1, R2, R3, R9, R12,
@@ -1426,21 +1422,21 @@ let isCall = 1, isTerminator = 1, isReturn = 1, isBarrier = 1 in {
     def TCRETURNri : PseudoInst<(outs), (ins tcGPR:$dst, variable_ops),
                        IIC_Br, []>, Requires<[IsDarwin]>;
 
-    def TAILJMPd : ABXI<0b1010, (outs), (ins brtarget:$dst, variable_ops),
-                   IIC_Br, "b\t$dst  @ TAILCALL",
+    def TAILJMPd : ARMPseudoInst<(outs), (ins brtarget:$dst, variable_ops),
+                   Size4Bytes, IIC_Br,
                    []>, Requires<[IsARM, IsDarwin]>;
 
-    def TAILJMPdt: ABXI<0b1010, (outs), (ins brtarget:$dst, variable_ops),
-                   IIC_Br, "b.w\t$dst  @ TAILCALL",
+    def tTAILJMPd: tPseudoInst<(outs), (ins brtarget:$dst, variable_ops),
+                   Size4Bytes, IIC_Br,
                    []>, Requires<[IsThumb, IsDarwin]>;
 
-    def TAILJMPr : AXI<(outs), (ins tcGPR:$dst, variable_ops),
-                     BrMiscFrm, IIC_Br, "bx\t$dst  @ TAILCALL",
-                   []>, Requires<[IsDarwin]> {
-      bits<4> dst;
-      let Inst{31-4} = 0b1110000100101111111111110001;
-      let Inst{3-0}  = dst;
-    }
+    def TAILJMPr : ARMPseudoInst<(outs), (ins tcGPR:$dst, variable_ops),
+                     Size4Bytes, IIC_Br,
+                   []>, Requires<[IsARM, IsDarwin]>;
+
+    def tTAILJMPr : tPseudoInst<(outs), (ins tcGPR:$dst, variable_ops),
+                     Size4Bytes, IIC_Br,
+                   []>, Requires<[IsThumb, IsDarwin]>;
   }
 
   // Non-Darwin versions (the difference is R9).
@@ -1455,21 +1451,20 @@ let isCall = 1, isTerminator = 1, isReturn = 1, isBarrier = 1 in {
     def TCRETURNriND : PseudoInst<(outs), (ins tcGPR:$dst, variable_ops),
                        IIC_Br, []>, Requires<[IsNotDarwin]>;
 
-    def TAILJMPdND : ABXI<0b1010, (outs), (ins brtarget:$dst, variable_ops),
-                   IIC_Br, "b\t$dst  @ TAILCALL",
+    def TAILJMPdND : ARMPseudoInst<(outs), (ins brtarget:$dst, variable_ops),
+                   Size4Bytes, IIC_Br,
                    []>, Requires<[IsARM, IsNotDarwin]>;
 
-    def TAILJMPdNDt : ABXI<0b1010, (outs), (ins brtarget:$dst, variable_ops),
-                   IIC_Br, "b.w\t$dst  @ TAILCALL",
+    def tTAILJMPdND : tPseudoInst<(outs), (ins brtarget:$dst, variable_ops),
+                   Size4Bytes, IIC_Br,
                    []>, Requires<[IsThumb, IsNotDarwin]>;
 
-    def TAILJMPrND : AXI<(outs), (ins tcGPR:$dst, variable_ops),
-                     BrMiscFrm, IIC_Br, "bx\t$dst  @ TAILCALL",
-                   []>, Requires<[IsNotDarwin]> {
-      bits<4> dst;
-      let Inst{31-4} = 0b1110000100101111111111110001;
-      let Inst{3-0}  = dst;
-    }
+    def TAILJMPrND : ARMPseudoInst<(outs), (ins tcGPR:$dst, variable_ops),
+                     Size4Bytes, IIC_Br,
+                   []>, Requires<[IsARM, IsNotDarwin]>;
+    def tTAILJMPrND : tPseudoInst<(outs), (ins tcGPR:$dst, variable_ops),
+                     Size4Bytes, IIC_Br,
+                   []>, Requires<[IsThumb, IsNotDarwin]>;
   }
 }
 
diff --git a/test/CodeGen/ARM/call-tc.ll b/test/CodeGen/ARM/call-tc.ll
index a77aba0..4dc37aa 100644
--- a/test/CodeGen/ARM/call-tc.ll
+++ b/test/CodeGen/ARM/call-tc.ll
@@ -74,7 +74,7 @@ entry:
 ; CHECKT2: t7:
 ; CHECKT2: blxeq _foo
 ; CHECKT2-NEXT: pop.w
-; CHECKT2-NEXT: b.w _foo
+; CHECKT2-NEXT: b _foo
   br i1 undef, label %bb, label %bb1.lr.ph
 
 bb1.lr.ph: